Telegraph repeater system



March 22, 1960 D. E. FoLEY ErAL TELEGRAPH REPEATER SYSTEM original Filed oct. 2a, 1952 2 Sheets-Sheet 1 ArroR/VE March 22, 1960 D. E. FOLEY Erm.

TELEGRAPH REPEATER SYSTEM Original Filed Oct. 28. 1952 2 Sheets-Sheet 2 0.E.FOLEV Eh'. HANLEV nited States Patent() TELEGRAPH REPEATER SYSTEM Daniel E. Foley, Nutley, and Frank H. Hanley, Butler, NJ., assignors to American Telephone and Telegraph Company, a corporation of New York Original application October 28, 1952, Serial No. 317,334, now Patent No. 2,761,896, dated September 4, 1956. Divided and this application April 9, 1956, Serial No. 577,131

5 Claims. (Cl. 317-152) The present application is a division of application Serial No. 317,334 filed October 28, 1952, now Patent 2,761,896, granted September 4, 1956, and claim is hereby made to all equitable and legal rights derivable therefrom.

The present invention relates to telegraph repeater systems and particularly to polar relay circuits whereby a single regenerative repeater unit may be interconnected through a new circuit described herein and called hereinafter a director' circuit so that the single regenerative unit will serve to regenerate signals passing in each didirection through a half-duplex interconnection such as through trunk circuits interconnected at a teletypewriter switchboard or telegraph line circuits interconnected through a telegraph test board or telegraph service board. Formerly, two regenerative repeater units, one for each direction, were required for this service.

As heretofore arranged in half-duplex teletypewriter switchboard service, for instance, two regenerative repeater units were provided, one for regenerating the signals for each direction of transmission. The differences in the switching arrangements between the circuits as heretofore arranged and the present circuits may be understood from the following.

Let it be assumed that a calling teletypewriter subscriber in New York calls a subscriber in Los Angeles and that the call is routed through the Chicago teletypewriter toll switching station and further that regeneration is required. Instead of using a single toll cord circuit to interconnect the New York to Chicago trunk directly to the Chicago to Los Angeles trunk, as would be the case it regeneration were not required, the Chicago toii operator heretofore employed a first teletypewriter cord circuit repeater to connect the incoming trunk from New York to a regenerative repeater coupling circuit, which circuit would extend into the input of a first regenerative repeater unit. The output of the iirst regenerative repeater unit would extend through the regenerative repeater coupling unit to a second teletypef writer cord circuit repeater, which would in turn be patched to the Los Angeles trunk. Signals originating in New York would be regenerated in the first regenerative repeater unit before retransmission to Los Angeles. Service is on a half-duplex basis, that is, it is possible to transmit in only one direction at a time. In order to regenerate the signals originating in Los Angeles before transmission to New York another regenerative unit was furnished. The regenerative coupling unit was arranged so that signals 'incoming from Los Angeles through the second teletypewriter cord circuit passed into the regenerative repeater coupling circuit to the input of a second regenerative repeater unit. The output Of the second regenerative repeater unit passed through the coupling circuit and through the first teletypewriter cord circuit repeater and over the trunk to New York.

In the present arrangement a single regenerative repeater unit is employed to regenerate the signalsin both ice directions. On such a call, on which regeneration is required, two teletypewriter cord circuit repeaters and a regenerator coupling circuit are employed in the same manner as formerly. However, the coupling circuit is arranged to perform an added function, namely, to direct the signals incoming from either direction into the input of a single regenerator unit and to direct the output of the single regenerator unit into the opposite circuit from which the signals are being received. In order to perform this directing function a switch which discriminates between the sources from which the signals are being received and directs them to the opposite circuit is required and that is the added function of the new coupling Vcircuit or director circuit as it is presently named in recognition of its directing function.

A regenerative repeater unit is an expensive piece of apparatus. It is most widely used at present in teletypewriter switchboard service and to a lesser extent in private line service and the present invention will reduce the total number required by about one-half.

In the case of the interconnection of two telegraph line circuits in private wire service, as distinguished from trunk circuits in teletypewriter switchboard service, the two telegraph lines are connected directly through the single director circuits to the single regenerative repeater unit, no cord circuits being employed, and the operation of the single director circuit and the single regenerative repeater unit is essentially the same as for a teletypewriter switchboard connection.

The invention may be understood from the following description when read with reference to the associated drawings which taken together disclose preferred embodiments in which the invention is presently incorporated. It is to be understood, however, that practice of the invention is not limited to the specific embodiments disclosed herein but the invention may be practiced with other embodiments which will be readily suggested to those skilled in the art by the following disclosure.

In the drawings, Fig. 1 is an embodiment of the invention arranged for teletypewriter exchange service.

Fig. 2 is an embodiment of the invention arranged for private line service.

In the following description where values of constants are cited it is to be understood that the values are cited by way of examples as an aid in understanding the invention and the operation of the circuit of the invention is not limited to elements having constants of the cited values.

Refer now to Fig. 1 which shows at the left, a rectangle representing a toll trunk circuit to the east and a second rectangle representing a toll trunk circuit to the west. The elements of two teletypewriter switchboard or TWX cord circuit repeaters, 1 and 2, essential to an understanding of the invention are shown to the right of the trunk circuits. Each cord circuit repeater is connected at its left-hand end to a trunk. The upper or cord circuit repeater 1 and the lower or cord circuit repeater 2 are connected to the east and west toll trunk, respectively. Next in order toward the right on the drawing is shown a single director circuit to which the right-hand end of each of the cord circuits is connected. At the far right on the drawing is shown schematically a single regenerative repeater unit to which the right-hand end of the director circuit is connected.

Signals generated in TWX cord circuit repeater 1, in response to signals received from its connected east trunk, pass into the director circuit. The director circuit directs them to the input of the single regenerative repeater unit. Regenerated signals from the output of the regenerator are directed by the director circuit to TWX cord circuit repeater 2 and then pass through thetoll trunk circuit 3 to the west. Signals originating in the west trunk pass through TWX cord circuit repeater 2 and through the director circuit into the input of the single regenerative repeater unit. The output of the single regenerative repeater unit is then directed through rEWX cord circuit repeater 1 to the connected east trunk. The single switch in the directing circuit, in the present embodiment, is a polar relay which has two control or operating elements namely, the -tirst and second operating windings connected to a iirst and a second telegraph channel. ri`he switch hasv two switch elements responsive to the operating winding controls, namely, a first and a second relay contact, which directs the outgoing regenerated signals toward the opposite telegraph signal channell from which they were received.

Regenerative repeaters are well known in the art. Their function is to reshape and retime distortedV telegraph or teletypewriter signals. To do this, advantage is taken of the fact that whereas the beginningsand ends of such signals may be distorted, the center portion aords atV least a reliable indication of the nature of the signal, that is to say, in the case of current-no-current signals, the center portion of a signal, if a current signal, will have suicient amplitude to operate a sensitive magnetic relay, for instance. By delaying the sensing of the nature of a signal element until its middle portion arrives and then sensing it, it is possible through the use of an electromechanical transmitter, or an electronic regenerative, re-

peater which transmits signals of standard duration, atk

the expense of a delay rof approximately ,one-half a signal element, to transmit a signal element of standard dura.

tion and perfectly shaped.V VEach incoming signal ele. ment, thereforeLis sensed at its middle portion and asignal element Ofstandard duration and perfect shapeistl'ien.

transmitted. lt is to be understood, of course, tn`at each` of the signal elements of a regeneratedwtrain of signal For a detailed description of the operation of a re,

generative repeater of the electromechanical type, see

W. r. Rea,Y Parent 2,337,496, issnailneceinher I2-1, 1943,

or W. I, Zfenner PatentA 2,l05,l73, yissuedzllanuary l1, 1938, and for an electronic regenerative repeater, SeejW. T. Rea, Patent 2,487,l 81,`issued November ,8, 19.49 Which are incorporated herein by'reference as though fully set'.

forth herein.V The present invention is operative Ywith the regenerative repeaters described in the foregoing patents as well as with other types of regenerative repeaters.

To consider now the detailed operation of the circuit per Fig. l, when the plug 1 of TWX cord circuit repeater 1 is connected to jack 2 of the director circuit, battery 3 on the sleeve of plug 1 is `connected through the sleeve of jack 2 and the winding of relay 4 to ground, operating relay 4iand closing ycontact 5. A circuit may then be. traced from ground throughrthewinding Yof relay 6,and contact of relay, 4 to battery', operatingA relay 6 'and closing contactsrr'and, The closing offcontacts 7.' and; 8' establishes VVa ircuitifrom.fpftl'vtne'ii sourc'efthough coni-,1- tacts 7 and 8 to motory 10,"s'ta'rtin'g the motor; offtlietrerl' generative repeater. n

To anticipate,and to' describe the regenerative repeater briey, the motor 10 iscoupled through shaftl. and av friction clutch (not shown) to eccentric cam,l 12 which controls followerl 13 'which is pivoted atie. The top portion ofvfollower 13 isbiased to the left 'by spring 100.

and is actuated to the right by `a projection on cam 12A which engages a projection on the-bottom of follower 13 Just before the middle. porionvof l-a.-s1"'g"nal element isimi- "assenso pressed on receiving magnet 101 of the regenerator, releasing lever 102 which is pivoted at 15 and the righthand portion of which is then free to assume an elevated position if magnet 101 is energized or a lower position, under the influence of spring 163, if it is not. Responsively, contact tu@ is closed when the right-hand portion of lever 1912 is' elevated and contact 195 is closed when the right-hand portion of lever 102 is lowered. Immediately after the contact 194 or 195 is closed, follower 13 locks the right-hand end of leve-r 102, in its elevated or lower position, under the intluence of spring 196 and maintains the lock for the duration of a standard signal element. Then, the cycle is repeated. When Contact iS is closed,

' for the spacing condition, positive battery is connected from the output of the re enerative repeater through armature tl to conductor S8 and when Contact 1194 is closed for the marking condition, since there is no connection to Contact 104, conductor 53 is open.

From the foregoing it will 'neV apparent that the contact controlling lever 1%.?, of the regenerative repeater output-V is. permitted to be actuated by the middle portion of an incoming signal element only, and is then locked in the position determined by the middle portion of the incoming signal element for the duration of a full signal element. Thus while signals transmitted fromy the regenerator contacts 164 and 1&5 are of standard duratiom they are displaced and delayed by a fixed interval, equal to approximately one-half the duration of a signalV element, from, the time of reception of the corresponding signal eiernent by regenerator receiving relay 22.

Thetarmature of the polar. regenerativereceiving relay 22is normally biased toward the right to tend to engage with its spacing contactiby the effect of'current owingV from positivebattery through resistor 109 and the bottom winding of relay 22 to ground, and the biasing current will be effectivefto actuate. the armature. of rela;I Zifto engage its'. spacing contact 21 when its etect is dominant over the countereect of current iiowing in the top Windingofrelay 22 which tends toactuate its armature to engage its marking contact Ztl in a manner to be explained.

A marking signal incoming from the east trunk will impress positive battery on the left-hand end of conductor 25A in TWX cord circuit repeater l and the cir cuit extends through the winding of polar relay 26 to ground, actuating the armature of relay 2n, to engage its marking contact 27. A circuit may then be traced from positivetbattery through ,marking contact 27 to junction Zwheiie it divides. One branchextend-s through the bottom or biasing winding 'ofrelay 30 to ground. The

eiect Vof current owing in this path tends to actuate the.

armature of relay 3i? toward the left to engage its spacing contact 32' but it is ineffective at present. branch of the circuit extending from 'junction 2S may be traced through the top winding of relay 39, resistance 'i3 tip of plug 1, tip of jack 2, resistance 3e, top winding of polar relay 36, resistance 37, junctionV 38, and top winding of polar relay 22 to negative battery. The eiect of the current flowing in the top winding of relay 3i) is dominant over the eifect of the current owing in itsk gage its contactV 42, but it will be ineffective for reasons to be explained hereinafter. The ZO-'miliiampere current from cord circuit repeater 1 will flow through the top Winding of relay 22.

For the marking condition, current from positive bat tery will iow from the ywest trunk through conductor Si and the windingofpolarrrelay 5,2 to ground, actuating the armature of relay 52 to engage with itsV right-hand or marking'contact 53. A circuit may then be traced from positivebattery through marking'c'otact' 53to junc= The otherr tion 55 where it divides. One branch extends through the bottom or biasing winding of polar relay 47 to ground. The effect of current flowing in this path tends to actuate the armature of relay 47 to engage its spacing Contact 49, but is ineffective at present. From junction 55 the other branch of the circuit extends through the top winding of relay 47, resistance 46, tip of plug 56, tip of jack 45, resistance 44, bottom winding of relay 36, resistance 39, junction 33 and the top winding of relay 22 to negative battery. It will be assumed that current of 20 milliamperes ows in the path last traced. its effect in the top winding of relay 47 is dominant over the opposing effect of current in the bottom winding of relay 47 and the armature of relay 47 is, therefore, maintained in engagement with marking contact 48 for the marking condition. The 20 milliamperes owing in the bottom winding of relay 36 oppose the effect of the 20 milliamperes flowing in the upper winding of relay 36. The effects are equal and opposed and, therefore, the ow of the 20milliarnpere current in the top and bottom windings of relay 36 will have no effect on the armature of relay 36 for the marking condition. The armature of relay 36 may float between the contacts, as indicated, or engage contact 41 or 42 for the marking condition of the system, and it will be without effect for reasons which will become apparent hereinafter.

The ZO-milliampere current fiowing in the top winding of relay 22 from cord circuit repeater 2 for the marking condition augments the effect of the 20-milliampere current flowing through the top winding of relay 22 from cord circuit repeater 1 for the marking condition. The effect of the combined 40-milliarnpere current in the top winding of relay 22 will be dominant over the counter'- effect of the 30-milliampere current in the bottom or biasing winding of relay 22 and the armature of relay 22 will, therefore, be actuated to engage its left-hand or marking contact 20, as shown, for the marking condition. 1 When the armature of relay 22 engages its left-hand or marking contact a circuit may be traced from positive battery through the armature and marking contact 20 of relay 22 and the winding of regenerative receiving magnet 101to ground energizing the magnet which will have the effect of closing the regenerative repeater output marking contact 104, as explained, after the delay. The armature of relay 36 is interconnected by conductor 58 to the armature 115 on lever 102. Attention is called to the fact that when the armature 115 of the regenerative repeater engages its marking contact 104, since there is no connection to contact 104, the circuit is open. For the marking condition of the system there fore, whether or not the armature of relay 36 engages contact 41, 42, or floats between them is immaterial.

It will now be assumed that the east trunk starts to transmit. In response to the first spacing signal element, the armature of relay 26 will be actuated to the left to engage its spacing contact 29. This substitutes negative battery for positive battery on the left-hand end of the circuit traced through the top Winding of relays 30 and 36. Since the top Winding of relay 22 is terminated in negative battery also, no current will fiow through the top winding of relays 30 and 36. Further, no current will ow from cord circuit repeater 1 through the top winding of relay 22. K

With respect to relay 30, since the polarity of the current fiowing through its bottom Winding is now reversed, its effect will maintain the armature of relay 30 in engagement with its marking contact 31. With respect to relay 36 the effect of the current tiowing in its bottom winding will now be unopposed and its armature will be actuated under the inuence of its bottom winding to engage itscontact 41. With respect to relay 22; when the current in its upper Winding is reduced to 20 mils, the effect of the 30-mil current in its lower or biasing winding becomes dominant and the armature of ,relay 22 is actuated to engage its spacing contact 21.

This disconnects battery from the winding of magnet 101 deenergizing it for the spacing condition.

It will be assumed that the magnitude of resistor 109 is 4000 ohms and the magnitude of resistor 111 is 6000 ohms. When the armature of relay 22 engages its spacing contact 21, resistors 109 and 111 are connected in parallel, both in series with the bottom winding of relay 22. This increases the current in the bottom winding from 30 milliamperes to 50 milliamperes. Since the current in the top winding is 20 milliamperes and its effect is in the marking direction and the current in the bottom winding is 50 milliamperes and its effect is in the spacing direction the net effect is that of 30 milliamperes in a direction to lock the armature of relay 22 against its spacing contact 21.

After an interval equal approximately to one-half the duration of a signal element, follower 13 will release lever 102 which will thereupon be actuated by spring 103 so that armature 115 engages its spacing contact 105, connecting positive battery through contact 105, armature 115, conductor 58, contact 41, junction 43, resistance 44, tip of jack 45, tip of plug 56, resistance 46, top winding of relay 47, junction 55 and the armature and marking contact 53 of relay 52 to positive battery. Positive potential of equal magnitude is connected to each end of this path. ln effect positive battery is connected directly to junction 43 so that no current flows through the top winding of relay 47. The effect of the current fiowing in the bottom winding of relay 47 will actuate its armature to engage its spacing contact 49 thereby transmitting a spacing signal to the connected trunk. While the spacing signal transmitted from contact 105 persists a path extends from junction 43 on which positive potential from contact 105 is impressed through the bottom winding of relay 36, resistance 39, junction 38 and the top winding of relay 22 to negative battery. This increases the current flowing in the bottom winding of relay 36 and in the top Winding of relay 22 t0 40 milliamperes, for instance. This locks the armature of relay 36 in engagement With its contact 41 for the duration of a standard full length spacing signal element being transmitted from contact 105 and prevents any interference with its transmission in the event that the armature of relay 26 is actuated to engage its marking contact 27 in response to the reception of a marking signal element while the latter half of the regenerated spacing signal is being transmitted.

During the transmission of the first half, approximately, of the spacing signal element from contact 105, the augmenting of the ZO-milliampere current flowing in the bottom winding of relay 36 with 20 additional milliamperes, as described, is unnecessary, because since there is no current flowing in the top Winding of relay 36, as the last half of a spacing signal element is being received from cord circuit repeater 1 and no current ows in the top winding for this condition, the normal ZO-milliampere current owing in the bottom winding of relay 36 would be more than adequate to hold the armature of relay 36 in engagement with contact 41. However, before the delayed spacing signal has been completely transmitted from contact 105, in the event that the succeeding signal element received from cord circuit repeater 1 is a marking signal element, the armature of relay 26 will reengage contact 27. Then 20 milliamperes will flow again through the top winding of relay 36 in a direction such that its effect tends to actuate its armature to engage contact 42. The armature of relay 36 must be maintained on contact 41, however, until the transmission of the delayed spacing signal element from contact 105 is completed in order to properly direct it into the trunk to the west. The now augmented current of 40 milliamperes, the effect f which is tending 4to maintain the armature of relay 36 in engagement with contact 41 will be effective, therefore, to prevent a succeeding marking signal element from cord circuit repeater 1 from preventing the transmission of the full length delayed spacing signalv element from'.-

contact 195. The augmenting of the -milliampere cur rent in thev top` winding; of relayl 22S with 20. additional milliamperes during, the interval. while the rst; half.v of

the` spacing 'signal element isb'eing transmitted' removes the locking current in. relay 2-2 by reducing the effective spacing current from 30 milliamperestoI 1'0 milliamperes or the difference between Smilliamperes spacingV and 4.0` milliamperes marking, rather thanA 50 milliamperes spacing and 20 milliamperes marking.

If the next` succeeding. signal element received from cordcircuit repeater. l isa marking` signaly element, current of 2Q milliamperes will iiow through the top winding of relay 36. Its effect willbe: in adirection toY tend to actuate the armature of relay 36 to engage its contact 42. As long as the regenerated spacing signal element continues. to bev transmitted from contact MBS, however,

36 and 20 milliamperes will dow through its top winding.

These two currents will combine and flow through the top winding of relay 22. Their combined etect of: 601 milliamperes tends' to actuateV the armature of relay 22:

to engage its marking contact 2t? and thet magnitude of theeffect is dominant over the counter or biasing effect` of. the 50 milliamperes in the bottom winding of relay 2`2and the armature of relay 22 will be actuated to engage its marking Contact 2G.

At the instant that the armature of relay 22 leaves its spacing contact 21, t e shunt path through resistance-111 is disconnected and the current through the bottom or biasing winding of relay 22 is reduced troni 50 milliamperes to 39 milliamperes. This increases the effective marking current from l() milliamperes to 30 milliamperes or from 60 minus 5G to 60 minus 30 milliamperes. This locks the armature of relay 22 to its marking contact 20. When the armature of relay 22 reengages its contact 2Q, it again energizes magnet lill. The Jt'ollower 13 will not be released by cam 12 until 'after a full length spacing signal element is transmitted, however. At the'termination of the transmission of. the delayed spacing signalV element, marking contact we of the regenerator will again be closed tin-.transmit the marking signal element to thev west trunk circuit. As soon as armature. 115 breaks from spacing contact 1&5, the potential impressed through contact li on terminal 43 will be disconnected. The current conditions prevailing in the top and bottom winding of relay 36 at the beginning will be restored, namely 20 milliamperes flowing in each winding of relay No matter what position is assumed bythe armature of relay Se during the transmission of the marking signal element from Contact i104, it is immaterial, as there is nothing,V connected to contact we during a marking interval.

During the reception of the latter-'half of amarking sigwilltbe transmitted therefrom to 'the connected t i against contact 4,1V throughout the interval that theyareV being transmitted from contact M5.

Themanner in which the system operatesV when sig; nais Vare received from the west trunk through; cordv circuit repeater 2 corresponds to that described in. the` foregoing for their reception from the east trunk through cord circuit repeater During the interval. while spac ing signals are being received from cord circuit .repeater 2 and while they are being transmitted from regenerator output contactsY lila and 10S, the armature of relay`36- will be maintained. in engagement with contact 42which, it will be observed, istconnected in parallel to the main transmission conductor of cord circuit repeater 1 and the4 top winding of relay 36, in a manner corresponding t0, that in which contact 41 is connected to themain trans mission conductor to cord circuit repeater 2 and tothe.. bottom winding of relay 36, so as to perform the correa sponding function of directing the output of theregenr. erator to the opposite cord circuit repeater from. which the signals are being received, in this case to cord circuit repeater 1, and to maintain the armature of relay 36 locked to contacts 42, as a result of augmented current.- in the top winding of relay 36, from4 contact l05, during the interval while the first half of a succeeding marking-k signal element is being received vfrom repeater 2.

The condenser 6% and resistance 61 connectedin series'- areV arranged as a Contact protecting shunt for contact. 1.195 and serve also as a` wave-Shaper. to shape the wave ofthetransmittedv signal to eliminate marking biascaused. by travel. time of armature 115.

For transmission in either direction, as a practical mat' ter, if relay 35 Vis unbiased, and otherwise in good. ad.-Y justment, its armature will be operated only once for each.- change in direction of transmission, that is= it will remain on the contact to whichY it is rst operated in response to; a change in the direction of transmission, say from east to west or from west to east, until the direction oftransmission is reversed.

Refer now to Fig. 2. Fig. 2 shows the arrangement of the circuits when they are connected for private line service as distinguished from teletypewriter switchboard service as in Fig. l.

In the arrangement per Fig. 2,v a telegraph line, line l, say from the `west, indicated byV a rectangle atrthexupperf left of Fig. 2 is connectedV through a terminating circuit and a director circuit to the single regenerativeunit. Another telegraph line, line 2 indicated by a. rectangle shown at thelower left is similarly connected tluoughan individual terminating circuit and the common director circuit to the single regenerative unit.

Except for minor differences the circuit connections and operation is identical with that of Fig. l. Onediif ference is that the polarity of the batteries connectedxto 36 with their effects opposing, or a net effect of zero. Y

the marking and spacing contacts of relays 25 and 52 in Fig. 2 is reversed from that connected to the correspond ing relays in Fig. l. Anotherv is that the polarity oithe; battery connected to the right-hand terminal of the top winding of relay 22 in Fig. V2 is opposite from that of vthe corresponding connection in Fig. l. Another difference is thatr battery' is connected to. the contacts. .ofsrelayf'd Thesechangesare made to match the ditterencein battery.YV

poling employed in private line operation irt a-welhknowrr large telegraph plant. Another diierence is the'employ.- ment of the parallel combination of non-linear resistance Y DRl, which may be, for instance, a dry rectifier, andresistor oinseries with .line i andacorresponding par# allel circuit comprising non-linear resistance- DR2 and resistor 122 in series with line 2. These-are provided so vthat the magnitude of the resistance'infserieswithfzthe repeater receivingY from the regenerative'` unit mayfbefthe" Asame for marking asfor spacing signals.

The operation of the circuit per Fig. 2 is practically identical with that described for the operation of Fig. 1.

One of the important features of the present invention is the locking feature of the receiving relay 22 for both marks and spaces which provides the equivalent of point selection because once the armature of receiving relay 22 is operated from one contact to the other it is locked to the operated contact until the output circuit of the regenerative repeater is locked by follower 13. T his feature increases the distortion tolerance of the regenerative unit, because after the armature of relay 22 locks, it will not be aected by distortion or the incoming signals received. in its upper winding. This increases the ield of application of the present invention to include circuits having a larger amount of incoming signal distortion than would otherwise be possible.

What is claimed is:

1. A polar relay having an armature, an operating winding and a biasing winding thereon, a rst closed circuit path including a source of potential and extending through a rst resistor in series with said biasing winding when said armature is in a first position and a second closed circuit path including said source of potential and extending through said armature and a second resistor connected in parallel with said first resistor and in series with said biasing winding responsive to the operation of said armature to a second position, to increase the current in said biasing winding.

2. A polar relay having an armature and a first and a second winding, a lirst closed circuit path including a source of potential and extending through a resistor in series with said first winding, when said armature is in a first position, and a second closed circuit path including said source of potential and extending through said armature and a second resistor connected in parallel with said lirst resistor, so that said first and said second resistors in parallel are connected in series with said first winding, responsive to the operation of said armature to a second position.

3. In a regenerative telegraph repeater system, a locking circuit for a polar receiving relay for a regenerative repeater, said relay having an armature thereon, said locking circuit comprising a irst closed circuit including a source of potential and extending through a first resistor and a Vwinding on said relay and a second closed circuit including said source of potential and extending through a second resistor, in parallel with said first resistor, both in series with said winding, said second circuit including said armature, said second circuit establishable responsive to the operation of said armature to a particular one of two positions to increase the current in said winding, so as to lock said armature in said particular position.

4. A polar relay, an armature and a Winding on said relay, a lirst closed circuit path having a source of potential and including said winding,.and means for increasing the current through said winding, said means comprising said armature and a rearrangement of irnedance elements in said circuit responsive to the operation of said armature to a particular position.

5. A polar relay, an armature thereon, a winding thereon, a iirst closed local circuit path extending from a source of potential through said winding at a first time, current of a rst magnitude greater than zero, iiowing from said source through said winding at said first time, a second closed local circuit path extending from said source through said winding at a second time and means in said second path for increasing the current through said winding responsive to the operation of said armature, said means comprising a shunting impedance interconnected Lrtough said armature between said source and said wielding.

References Cited in the tile of this patent UNITED STATES PATENTS 2,134,820 Hanley Nov. 1, 1938 2,539,551 Rea Jan. 30, 1951 2,598,669 Battilana June 3, 1952 2,677,016 Davey Apr. 24, 1954 

